Controlled fluid delivery in a microelectronic package

ABSTRACT

A microelectronic package includes a die which may include MEMS and CMOS circuitry for analyzing a fluid. A defined path is provided for channeling fluid to the die. Rather than patterning depressions or physical channels in the package substrate, the defined paths comprise coatings that may channel the flow of liquids to the die for biological sensor type applications. The defined paths may comprise a wetting coating that has an affinity to fluids. Similarity, the defined paths may comprise a dewetting coating the tend to repel fluid surrounding the paths.

CROSS-REFERENCED TO RELATED APPLICATIONS

The present application is a divisional of U.S. patent application Ser. No. 11/966,560, filed Dec. 28, 2007.

FIELD OF INVENTION

Embodiments of the present invention relate to fluid delivery and, more particularly to micro-fluid delivery to a silicon die for example, for biological sensor applications.

BACKGROUND

Recently, there has been a growing interest for those in the health fields for developing biosensors, molecular libraries, Lab-on-a-Chip (LOC), and other biological electronic and bio-MEMS based devices. Lab-on-a-chip (LOC) refers to devices that integrate multiple laboratory functions on a single chip. Such chips are capable of managing extremely small volumes of fluid, for example, in the range of pico-liters or less. LOC generally involves the scaling of single or multiple lab processes down to chip-format to perform chemical analysis. Many uses are possible for LOC devices such as immunoassays to detect bacteria, viruses and cancers based on antigen-antibody reactions; dielectrophoresis for detecting cancer cells and bacteria, or blood sample analysis.

Controlled fluid delivery to a semiconductor die is of utmost importance for such biological sensor applications. Generally this delivery involves creating physical channels or trenches in a substrate in which the fluid may travel to reach the die where chemical analysis may be performed.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like parts throughout the various views unless otherwise specified:

FIG. 1 is a plan view of a microelectronic package or lab on a chip (LOC) according to one embodiment of the invention;

FIG. 2A is a plan view of the microelectronic package illustrating the microfluidic circuitry according to an embodiment;

FIG. 2B is a side view of the package shown in FIG. 2A;

FIGS. 3A, 3B, and 3C show the steps for patterning the wetting/dewetting coatings to form the fluid flow channels within the package; and

FIGS. 4A and 4B show an experiment using microscope slides to demonstrate the viability of using wetting/dewetting coatings to form fluid flow channels.

DETAILED DESCRIPTION

Described is a microelectronic packaging scheme for controlling the delivery of fluids to one or more silicon devices which may comprise biological sensors, molecular libraries, MEMS devices and/or other applications involving interaction with a fluid. Embodiments eliminate the need for creating physical channels via methods such as milling, etching, etc. in the package with the ability to deliver controlled amounts of fluids to a chip for biological applications. Embodiments enable rapid, low cost assembly of packaging comprising complex microfluidics control. Embodiments also enable the use of clear quartz, polyester, or polycarbonate lids or covers which provide access to the silicon device for inspection by visual and/or spectrometric methods, such as UV light, IR light, laser, etc.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

Referring now to FIG. 1, there is shown a simplified view of a Lab on Chip (LOC) according to one embodiment. In its simplest form the LOC comprises a substrate 100 including a die 102, which may include MEMS and CMOS circuitry for analyzing a fluid, a package cover 104, a coating defining a path 106 in which a fluid may travel to reach the die 102, and a fluid delivery mechanism 108. Here the fluid deliver mechanism 108 is shown as a simple dropper. However, the fluid deliver mechanism may also be a pump or MEMS device which may or may not be integral with the LOC.

Rather than patterning depressions or physical channels in the substrate 100, the defined paths 106 comprise coatings that may channel the flow of liquids to the die 102 for biological sensor type applications or other application. The defined paths 106 may be coated with a wetting coating that has an affinity to fluids. Similarly, areas on the substrate 100 and package cover 104 not in the defined path may have a dewetting coating that tends to repel fluids.

Referring now to FIGS. 2A and 2B, there is shown a plan view and a side view, respectively, of one embodiment of the invention. The device may comprise a substrate 200 and a cover 202 to fit over the substrate 200. One or more fluid inlets 204 may be provided on an edge of the substrate 200 into which a fluid may be introduced. In addition, one or more microfluidic channels 205 may be patterned adjacent to the fluid inlets 204 to carry the fluid to a die 208.

The die 208 may comprise various microfluidic circuitry 210 that may comprise various CMOS and MEMS devices for analyzing the fluid. Spacers 212 may be provided between the cover 202 and the substrate 200 to allow clearance for the fluid to move. The fluid may move by capillary action through the microfluidic channels 206 to the die 208. As best shown in FIGS. 2b , the channels 206 may comprise a wetting fluid coating 214 stamped or otherwise patterned on the substrate 200 and the cover 202.

A wide variety of fluids may be used such as water, alcohols, solvents such as toluene, acetone, etc. containing the biological molecules. The substrate 200 or cover 202 may comprise glass, quartz, ceramic, organics etc. such that it is optically, UV, or IR transparent, or electrically/thermally conductive to allow detection of biomolecules or allowing detection by any other methods known in the art.

Examples of useful wetting coatings 206 include monolayers, such as trimethoxysilane surfactants, thiol surfactants, alcohol surfactants, and the life. Similarly, dewetting materials such as silica, titania and the like, may be used outside the channels 206 which are neat, dispersed in solvents or in a polymer matric such as epoxy, polyimide, polyester etc. A wide variety of methods may be used to place the dewetting/wetting coating in the desired locations, including subtractive methods, such as UV lithography, additive methods, such as soft lithography, and other methods known in the art.

FIGS. 3A, 3B, and 3C illustrate a method for producing an embodiment of the invention. As shown in FIG. 3A, the die 208 is located in the substrate 200. A patterned stamp 300 containing the wetting/dewetting coating 214 may be used to stamp or otherwise plac eth ecoating 214 onto the substrate 200 in the desired pattern for form the channel or flow path 206. Likewise a stamp 300 may produce a corresponding patterned coating 214 on the cover or lid 202 as shown in FIG. 3B. Placement of the top lid or cover 202, analogously patterned with a corresponding flow path 206 is separated from the substrate 200 by a spacer 212.

The substrate 200 may be designed such that there is a hollow etched in to create a space for the die 208 such that the die 208 is flush with the top of the substrate 200. The microfluidic channels 210 in the die 208 then line up with the channels on the substrate 200.

In one embodiment of the invention, the dewetting coating is a nanocomposite comprising silica nanoparticles in epoxy resin. The coating is placed on the substrate using a patterned stamp 300 in regions where fluid flow is not desired. An analogous coating is placed on another substrate which will act as the top surface. This surface is placed on the bottom substrate with a spacer 212 in between.

In another embodiment of the invention, the dewetting coatings are alkoxysilanes such as octadecyltrichlorosilane, heptadecafluoro 1, 1, 2, 2, tetrahydrodecyl trichlorosilane and alkanethiolates such as n-alkanethiol. The microfluidic channel is achieved by selective UV degradation of the coating or by using a patterned stamp inked with the coating and stamping onto the substrate, or by other methods known in the art.

In another embodiment of the invention, wetting coatings such as nanoparticles such as silica, titania, etc. neat or dispersed in solution, nanocomposites such as functionalized silica in epoxy resin etc. or carboxylic acid terminated silanes etc. are utilized. The coatings are stamped onto the substrate using a patterned stamp such that the coatings in this case comprise the microfluidic channel.

It is apparent to those skilled in the art that the micoelectronic packages of this invention may comprise multiple channels or channels comprising complex pattern for splitting the fluid sample. If desired, additional fluid flow control devices may be incorporated into the package of this invention, including gates, pumps, suction, and the like.

FIGS. 4A and 4B are provided to show an experiment using microscope slides to demonstrate the viability of using dewetting coatings to form fluid flow channels. Controlled fluid flow is demonstrated using two glass microscope slides placed over each other with a spacer in between. The glass slides are cleaned with isopropyl alcohol. A dewetting coating (water contact angle 120°) is applied on a glass microscope slide in a defined pattern .A corresponding pattern is applied on a second glass slide. A spacer of about 150 μm is placed between the slides and the top slide is placed such that the dewetting patterns on both the slides correspond. Colored water is injected on one side and flows through the. The water flows only in the regions where there is no coating. FIG. 4A illustrates the glass slides before injecting water and FIG. 4B after injecting showing the controlled flow of water. One will notice the fluid flowed was confined to the defined channel path using the coatings with no need to form a trench as is typically done.

The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to be precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.

These modifications can be made to the invention in light of the above detailed description. The terms used in the following claims should not be construed to limit the invention to the specific embodiments disclosed in the specification and the claims. Rather, the scope of the invention is to be determined entirely by the following claims, which are to be construed in accordance with established doctrines of claim interpretation. 

We claim:
 1. A method for forming virtual fluidic channels on a substrate to channel a fluid to a die, comprising: providing a die on a substrate, the die including one or more fluidic circuits; patterning a coating on the substrate to define a fluid path from an edge of the substrate to the die: patterning a coating on a cover corresponding to the fluid flow path; positioning a spacer on the substrate; and placing the cover over the substrate and the spacer, wherein the coatings define a virtual fluidic path to channel a fluid to the die.
 2. The method of claim 1, wherein the patterning comprises stamping the substrate and the cover with a stamp having the coating thereon.
 3. The method of claim 1, wherein the coating comprises a wetting coating within the fluid flow path.
 4. The method of claim 3, wherein the wetting coating comprises nanoparticles including silica or titania.
 5. The method of claim 1, comprising providing a dewetting coating surrounding the fluid flow path.
 6. The method of claim 5, wherein the dewetting coating comprises one of alkoxysilanes and alkanethiolates.
 7. A system, comprising: a substrate having a die positioned thereon including CMOS and MEMS circuits for processing biological fluids; a cover over the substrate; and a virtual fluid path comprising one of a wetting or dewetting coating patterned on the substrate and the cover for channeling the biological fluids from an inlet on an edge of the substrate to the die.
 8. The system of claim 7, wherein the wetting coating comprises nanoparticles including silica or titania within the fluid path.
 9. The system of claim 7, wherein the dewetting comprises one of alkoxysilanes and alkanethiolates surrounding the fluid path.
 10. A system, comprising: a substrate having a hollow defining space; a die positioned in the hollow defining space so that a top surface thereof is flush with a top surface of the substrate, and which includes CMOS and MEMS circuits and a fluidic channel for processing biological fluids; a cover over the substrate; and a fluid path including a first coating patterned on the substrate and a second coating patterned on the cover, wherein the first coating and the second coating respectively comprise a wetting coating within the fluid flow path, and the wetting coating comprises functionalized nanoparticles including any of silica in epoxy resin or titania; and a plurality of fluid inlet ports provided on an edge of the substrate and in line with the fluid flow path, wherein the fluid flow path is to channel the biological fluids from the fluid inlet ports to the die.
 11. The system of claim 10, further comprising a spacer between the substrate and the cover. 